Preheat oven to 425 degrees F.
Wash the potatoes well by scrubbing under water, dry with a towel, and pierce tiny holes all around the potato with a fork. Wrap up each potato in aluminum foil and place on a baking sheet.
Bake in the oven at 425 degrees F for about 40 - 60 minutes. Check at 40 minutes by piercing a knife in the center. If the potato is tender and knife goes in smooth they are ready. The size of the potato will determine the baking time.
Mix together the maple syrup with walnuts and cranberries. Place on a separate baking sheet and roast for 10 minutes in the same oven with the potatoes.
Melt butter in a medium saucepan set over medium heat. When the butter begins to bubble (3-5 minutes), add in the minced garlic, and chopped sage leaves. Using a whisk, stir the mixture consistently for (2-3 more minutes) until the butter has turned a light brown color. You should begin to smell a rich and nutty aroma. This means it's ready!
Remove the cooked potatoes from foil and slice lengthwise. Top each one with a few roasted walnuts and cranberries. Drizzle each baked purple sweet potato with the sage and brown butter sauce. Salt and Pepper to taste!!